Hi @MalomgreWim-0803 ,
Thanks for your reply!
Based on my test, i can reproduce your case. In order to further confirm if the issue is related to Microsoft To Do, i have tried to open the task in Task tab in Outlook and i found it can be opened successfully in Onenote. So i'm afraid that the issue is related to Microsoft To Do. Please kindly understand that the Outlook tag here we mainly focus on general issues about Outlook desktop client. It's suggested that you could post your case in dedicated forum for Microsoft To Do for more professional advice.
If you want to open Onenote task in Outlook, it's suggested that you could click the apps icon and add task to access your tasks.
Hope to help you!
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